5.4. Math functions

Python has a math module that provides most of the familiar mathematical functions. Before we can use the module, we have to import it:

>>> import math

This statement creates a module object named math. If you print the module object, you get some information about it:

import math print(math)

The module object contains the functions and variables defined in the module. To access one of the functions, you have to specify the name of the module and the name of the function, separated by a dot (also known as a period). This format is called dot notation.

import math signal_power = 10 noise_power = 10 ratio = signal_power / noise_power decibels = 10 * math.log10(ratio) print(decibels) radians = 0.7 height = math.sin(radians) print(height)

The first example computes the logarithm base 10 of the signal-to-noise ratio. The math module also provides a function called log that computes logarithms base e.

The second example finds the sine of radians. The name of the variable is a hint that sin and the other trigonometric functions (cos, tan, etc.) take arguments in radians. To convert from degrees to radians, divide by 360 and multiply by 2pi:

import math degrees = 45 radians = degrees / 360.0 * 2 * math.pi result = math.sin(radians) print(result)

The expression math.pi gets the variable pi from the math module. The value of this variable is an approximation of pi, accurate to about 15 digits.

If you know your trigonometry, you can check the previous result by comparing it to the square root of two divided by two:

import math result = math.sqrt(2) / 2.0 print(result)

Q-5: Which statement allows you to use the math module in Python?

• import math
• Correct! import math allows you to use the math module by creating the "math" module object.
• include math
• Incorrect! include works similarly to import, but it's not what we're using. Try again.
• add math
• Incorrect! add will not import the math module. Try again.
• None. You can always use the math module.
• Incorrect! Something needs to be done to allow the math module to be used. Try again.

Q-6: To access a function in a module, we must use…

• log
• Incorrect! log is a function within the math module. Try again.
• quotation marks or single quotes
• Incorrect! You need these to create a string. Try again.
• dot notation
• Correct! Dot notation allows us to access a function in a module.
• function notation
• Incorrect! Function notation is the way a function is written. Try again.

Activity: CodeLens 5.4.8 (functMath_codelens1)

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